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Whitepaper: Networking Performance in Multiple VMs

Scaling and performance of VMware ESX Server 3.0.1 and XenEnterprise 3.2.0 are measured by running a heavy networking load simultaneously in each of several uniprocessor virtual machines. The results are also compared with a single SMP native machine running the same total load.

In a companion paper (Multi-NIC Networking Performance in ESX 3.0.1 and XenEnterprise 3.2.0, http://www.vmware.com/pdf/Multi-NIC_Performance.pdf) we looked at loading up a single virtual machine (VM) with multiple netperf instances, each running over its own NIC (Network Interface Controller). This effectively exposes the real virtualization overhead of high-throughput networking. While there are some real-world use cases that require this much network bandwidth in a single VM, a much more common scenario is spreading this bandwidth over many VMs running on one physical machine. This is a natural result of consolidating servers. For this paper we used the same hardware and software as in the multi-NIC paper, but performed a “scale-out” test: each of several VMs had a 1 Gbps physical NIC dedicated to it and each communicated to a similar dedicated NIC on the client machine through a netperf/netserver pair. The VMs did not share NICs. We hope this will lead to a better understanding of the performance issues involved with virtualizing networking.

By using up to four VMs/NICs here instead of the three NICs used in the earlier paper, we made better use of the 4-core server and were also able to test the scaling properties of each hypervisor. With dual- and quad-port network cards now commonly available, many users expect to be able to use four or more NICs even in low-end servers. Though the documentation included with XenEnterprise 3.2.0 indicates that the product supports only three physical NICs, the user interface had no problems configuring four NICs and issued no errors or warnings. Because of this ambiguity, and since this is such an important case, we included four-NIC benchmark results.  Users should always verify support for their desired hardware configurations. VMware ESX Server 3.0.1 supports 32 e1000 physical NICs.

You can read this 4-page whitepaper from VMware, here.

Published Sunday, June 10, 2007 8:03 AM by David Marshall
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